[NSRCA-discussion] Main battery redundant lead for receiver

[Keith Hoard]

Anthony,

   On a typical flight, I'm guessing the radio only uses around 100-150Mah
of power, while the motor is using 4000Mah, so that's about 4% more draw on
those two cells.  In practice, I haven't been able to see any difference in
the radio cells when I hook them up to my charger at the end of a flight.
Sometimes cells #1 & #2 are the high cells after a flight, so I think the
power draw of the radio is negligible to our motor packs.

The problem with two regulators plugged into the same 10S (or 5S) pack is
that you are creating a dead short between the cells thru the ground wires
(typically a straight wire thru the regulator).

Say you plug Regulator #1 into cells #1&2, and Regulator #2 into cells
#6&7.  The regulator's *ground *wires now have 5 cells of voltage potential
(5 X 4.2V = 21Volts) between them since they are plugged into cells # 1 and
#6.  When those two ground wires are then plugged into your receiver either
thru a switch or direct connection the magic smoke will escape and your
retailer will rejoice.

Also, if you have both of your regulators plugged into your motor pack and
the packs eject like Goose in Top Gun, you've lost both of your redundant
power sources.  However, if you use a tiny 2S LiPo that is physically
separated and secured inside your plane, you have both electrical and
physical redundancy.

Hmmm, just thought of something . . . maybe we should tie down the receiver
so the main regulator can't take the receiver out with it. . . so many
contingencies, so little weight . . .

Keith Hoard
Collierville, TN
khoard at gmail.com




On Tue, Jan 24, 2012 at 8:15 AM, Anthony Romano <anthonyr105 at hotmail.com>wrote:

>  Seems like a great idea but I have two questions. Do the packs come down
> out of balance since two cells are serving extra load? Is there a problem
> with parallel operation of two regulators?
>
> Thanks,
>
> Anthony
>
>  ------------------------------
> From: joddino at socal.rr.com
> Date: Mon, 23 Jan 2012 15:25:00 -0800
> To: nsrca-discussion at lists.nsrca.org
> Subject: Re: [NSRCA-discussion] Main battery redundant lead for receiver
>
> I've been using this setup for sometime and it is working great.  I have
> my two cell LiPo charged to 7.5 volts and it is connected to a 6.0 volt
> regulator into the receiver.  The cable connected to the balance connector
> on the "bottom" 5S is connected to a 6.3 volt regulator so it supplies all
> the current to the system and the 2S pack never needs charging.  I'm using
> an 800 mAh pack but it could be even smaller.
>
> Jim O
>
>
>  On Jan 23, 2012, at 2:09 PM, Scott McHarg wrote:
>
> Guys,
>    Chris Moon just e-mailed me about some leads that were done at the
> factory.  These leads run off your balance leads to a voltage regulator and
> allow your main battery pack to be utilized as a redundant receiver
> battery.  It is NOT meant to be a primary but it will save 20+ grams if
> you're running 2 rx batteries.  You still have to run the 2nd regulator for
> true redundancy but you eliminate the 2nd battery.  These leads are factory
> made and eliminate the need to make them yourself with the concern about
> plugging in to the wrong cell.  I know in my article, I was pretty much
> against doing this as a backup but, with Chris having this made at the
> factory, he has all but eliminated making a mistake by tying to the wrong
> cell.  I have the link that I'll e-mail you off-list or you can just go to
> his website.  I don't want to break the NSRCA list rules by advertising for
> him even though he advertises with the NSRCA.  The leads are only $3.99
> each and are found under the Connectors/Adapters listing.
>
> Thank,
> Scott
>
> --
> *Scott A. McHarg*
>
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